Zhang J, Nair I, Sahl J
Oak Ridge National Laboratory, Tennessee, USA.
Bioelectromagnetics. 1997;18(5):365-75.
The incomplete understanding of the relation between power-frequency fields and biological responses raises problems in defining an appropriate metric for exposure assessment and epidemiological studies. Based on evidence from biological experiments, one can define alternative metrics or effects functions that embody the relationship between field exposure patterns and hypothetical health effects. In this paper, we explore the application of the "effects function" approach to occupational exposure data. Our analysis provides examples of exposure assessments based on a range of plausible effects functions. An EMDEX time series data set of ELF frequency (40-800 Hz) magnetic field exposure measurements for electric utility workers was analyzed with several statistical measures and effects functions: average field strength, combination of threshold and exposure duration, and field strength changes. Results were compared for eight job categories: electrician, substation operator, machinist, welder, plant operator, lineman/splicer, meter reader, and clerical. Average field strength yields a different ranking for these job categories than the ranks obtained using other biologically plausible effects functions. Whereas the group of electricians has the highest exposure by average field strength, the group of substation operators has the highest ranking for most of the other effects functions. Plant operators rank highest in the total number of field strength changes greater than 1 microT per hour. The clerical group remains at the lowest end for all of these effects functions. Our analysis suggests that, although average field strength could be used as a surrogate of field exposure for simply classifying exposure into "low" and "high," this summary measure may be misleading in the relative ranking of job categories in which workers are in "high" fields. These results indicate the relevance of metrics other than average field strength in occupational exposure assessment and in the design and analysis of epidemiological studies.
对工频场与生物反应之间关系的不完全理解，给确定暴露评估和流行病学研究的合适指标带来了问题。基于生物学实验的证据，可以定义替代指标或效应函数，以体现场暴露模式与假设的健康效应之间的关系。在本文中，我们探讨了“效应函数”方法在职业暴露数据中的应用。我们的分析提供了基于一系列合理效应函数的暴露评估示例。使用几种统计方法和效应函数对电力公司工人的极低频（40 - 800赫兹）磁场暴露测量的EMDEX时间序列数据集进行了分析：平均场强、阈值与暴露持续时间的组合以及场强变化。比较了八个工作类别的结果：电工、变电站操作员、机械师、焊工、工厂操作员、线路工人/接线员、抄表员和文职人员。平均场强对这些工作类别的排名与使用其他生物学上合理的效应函数获得的排名不同。虽然电工组按平均场强计算暴露最高，但变电站操作员组在大多数其他效应函数中排名最高。工厂操作员在场强变化总数大于每小时1微特斯拉方面排名最高。文职人员组在所有这些效应函数中都处于最低端。我们的分析表明，虽然平均场强可以用作场暴露的替代指标，用于简单地将暴露分为“低”和“高”，但在对处于“高”场中的工人的工作类别进行相对排名时，这种汇总测量可能会产生误导。这些结果表明，除平均场强之外的指标在职业暴露评估以及流行病学研究的设计和分析中具有相关性。
